int my_strcmp(const char *s1, const char *s2)
{
	for (; *s1 == *s2;++s1,++s2)
	if (*s1 == '\0')//注意这里的*s1要与上一句的*s1一样
		return 0;
	return (*(unsigned char *)s1 < *(unsigned char *)s2 ? -1 : 1);//可以改成相减
}
